1. Field of the Invention
The present invention generally relates to optical detectors for optical fibre communications systems and in particular relates to self-aligning optical detectors for such systems.
2. Background of the Invention
A typical optical data communications system comprises a transmitter and a receiver interconnected by an optical fibre. The core diameter of the optical fibre is typically between 8 um and 60 um. At the transmitter, light is modulated by an electrical data signal to be transmitted. The modulated light is injected into one end of the optical fibre. The receiver, at the other end of the fibre, comprises a photosensitive transducer such as a photo-diode or photo transistor for converting incident light from the fibre back into the electrical data signal. It will be appreciated that efficient detection of the received light demands alignment of the end of the fibre and the photosensitive area of the transducer device. Conventionally, alignment is achieved mechanically. However, mechanical alignment requires significant skill and effort in view of the relatively small dimensions of the fibre and transducers. Also, the capacitance of the transducer increases as the photosensitive area is enlarged. As the capacitance of the transducers is increased, the response of the transducer is degraded correspondingly. Therefore, it is desirable to reduce the photosensitive area as far as possible in the interests of maximizing sensitivity.
U.S. Pat. No. 5,557,693 describes an optical communication system having a receiving optical sensor array and a transmitting optical sensor coupled together by a bundle of parallel optical fibres. In use an image is presented to one end of the bundle by the transmitting sensor array and received at the other end of the bundle by the receiving sensor array.